1. Field of the Invention
The present invention relates to a control method and control system for upshifting a compound semi-blocked splitter type automatic or semi-automatic transmission system. Automatic and semi-automatic mechanical transmission systems are known in the prior art and illustrated in U.S. Pat. Nos. 4,361,060 and 4,648,290, the disclosures of which are hereby incorporated by reference. Semi-blocked compound transmissions of the splitter type are known in the prior art and illustrated in U.S. Pat. Nos. 3,924,484; 4,735,109 and 4,736,643, the disclosures of which are hereby incorporated by reference.
2. Description of the Prior Art
Fully automatic transmission systems, both for heavy-duty vehicles such as heavy-duty trucks and/or coaches, and for automobiles, that sense throttle openings or positions, vehicle speeds, engine speeds, and the like, and automatically shift the vehicle transmission in accordance therewith are well known in the prior art. Such fully automatic change gear automated mechanical transmissions utilizing electronic and/or pneumatic logic and actuators to engage and disengage mechanical (i.e. positive) clutches to achieve a desired gear ratio. Examples of such transmissions may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,081,065; 4,361,060; 4,569,255; 4,576,065 and 4,576,263, the disclosures of which are hereby incorporated by reference.
Semi-automatic mechanical transmission controls wherein automatic changing between a plurality of gear ratios is provided while normally permitting the driver to choose when to make a particular gear ratio change, whether to select the immediately consecutive ratio up or down or to skip one or more ratios, and when to slip, i.e. to incompletely engage, the vehicle master clutch in a lower crawler gear are known. Furthermore, the semi-automatic control system prohibits engagement of a driver selected higher ratio, i.e. an upshift, that would cause the engine speed to decrease below the idle speed, i.e. would cause stalling and/or over-stressing at low speeds of the engine, and of a lower ratio, i.e. a downshift, if such a change would cause overspeeding of the engine. Examples of such a semi-automatic transmission control can be seen by reference to above-mentioned U.S. Pat. No. 4,648,290.
A control method for shifting automatic and semi-automatic mechanical transmissions (called "AMTs") including semi-blocked, splitter type compound transmissions wherein each shift, both simple (auxiliary section only) shifts and compound (main and auxiliary section) shifts, involves shifting of the main transmission section to neutral to allow shifting of the blocked auxiliary section without requiring a crossing of synchronous of the preselected jaw clutch members is disclosed in U.S. Pat. No. Re. 32,591, the disclosure of which is hereby incorporated by reference.
While shifting of AMTs including semi-blocked transmissions by the method of shifting the main section into neutral and then allowing the preselected blocked jaw clutches of the auxiliary section to unblock, usually under the influence of sensor unblocking ramps as disclosed in above-mentioned U.S. Pat. No. 3,924,484, without requiring/causing the preselected auxiliary section blocked jaw clutch members to "cross" or "pass-through" synchronous is acceptable for most operating conditions, under certain conditions due to frictional drags, actuation delays, cold operating conditions, and/or a requirement for a quicker and more positive shifting of the auxiliary section, the prior art shifting control method was less than totally satisfactory.